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Switching power supply

a technology of shunt resistor and power supply, which is applied in the field of switching power supply, can solve the problems of loss due to shunt resistor, low design of power gnd line on low potential side of switching device for connecting shunt resistor, and the cost of this shunt resistor, so as to reduce loss and eliminate current-detecting resistor

Inactive Publication Date: 2010-09-21
RENESAS ELECTRONICS CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

This solution reduces costs and losses associated with the shunt resistor, simplifies the power GND pattern design, improves reliability by stabilizing the gate voltage, and suppresses noise, while maintaining a high power factor correction efficiency.

Problems solved by technology

However, since a current-detecting resistor (hereinafter, it is called “shunt resistor”) is used in the conventional switching power supply, there are problems that a cost of this shunt resistor and a loss due to the shunt resistor occur.
In addition, there is a problem that the design of a power GND line on a low potential side of a switching device for connecting the shunt resistor is limited.

Method used

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Examples

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first embodiment

[0041]With reference to FIG. 1, a configuration of a switching power supply according to a first embodiment of the present invention will be described. FIG. 1 is a circuit diagram showing the configuration of the switching power supply according to the first embodiment of the present invention, showing a circuit diagram of a PFC converter as a switching power supply.

[0042]In FIG. 1, the switching power supply comprises: an input filter 2; a rectifier 3; a coil 5; a boost diode 6; a power MOSFET 8; a smoothing capacitor 9; voltage-dividing resistors 11a to 11h, a capacitor 12, and a control circuit 20.

[0043]The control circuit 20 comprises: a driver 17; a maximum Duty circuit 18; a switch 21; an output voltage regulator 22; an amplifier 23; a multiplier 24; a comparator 25; a clock 26; a flip-flop circuit 27; an OR circuit 28; and a delay circuit 30.

[0044]An AC power supply 1 is changed to an input voltage 4 via the input filter 2 and the rectifier 3 which is rectifying means to have...

second embodiment

[0080]Next, with reference to FIG. 1 and FIG. 4, a configuration of a switching power supply according to a second embodiment of the present invention will be described. FIG. 4 is a circuit diagram showing a configuration of a control circuit of the switching power supply according to the second embodiment of the present invention.

[0081]In the switching power supply of the present embodiment, the control circuit 20 of the switching power supply according to the first embodiment shown in FIG. 1 is replaced with the control circuit 20 shown in FIG. 4.

[0082]The control circuit 20 shown in FIG. 4 has a function similar to that of the control circuit 20 of the circuit diagram shown in FIG. 1, and the control circuit 20 in FIG. 4 operates in combination with a main circuit in FIG. 1 by replacing the control circuit in FIG. 1 with the control circuit 20 in FIG. 4. In FIG. 4, parts and blocks having the same functions as in FIG. 1 are applied with the same reference numerals.

[0083]Inside th...

third embodiment

[0103]Next, with reference to FIG. 1 and FIG. 5, a configuration of a switching power supply according to a third embodiment of the present invention will be described. FIG. 5 is a circuit diagram showing a configuration of a control circuit of the switching power supply according to the third embodiment of the present invention.

[0104]In the switching power supply of the present embodiment, the control circuit 20 of the switching power supply of the first embodiment shown in FIG. 1 is replaced with the control circuit 20 shown in FIG. 5.

[0105]The control circuit 20 shown in FIG. 5 has a function similar to the control circuit 20 of the circuit diagram shown in FIG. 1, and the control circuit 20 in FIG. 5 operates in combination with the main circuit in FIG. 1 by replacing the control circuit 20 in FIG. 1 with the control circuit 20 in FIG. 5. In FIG. 5, parts and blocks having the same functions as in FIG. 1 are applied with the same reference numerals.

[0106]In the control circuit 2...

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Abstract

A switching power supply capable of correcting a power factor without using a shunt resistor is provided. The switching power supply includes a rectifier for rectifying an AC power supply, boosting means including a power MOSFET for boosting an output of the rectifier, a smoothing capacitor for smoothing an output of the boosting means, voltage-dividing resistors for detecting a voltage between main terminals of the power MOSFET, a switch for selecting only the voltage by which the power MOSFET is in on-state from voltages detected by the voltage-dividing resistors, an amplifier for amplifying the voltage selected by the switch and outputting the same as a current corresponding value of a current flowing in the power MOSFET, voltage-dividing resistors for detecting the output voltage, and driving means which form a pulse signal based on the current corresponding value and the output voltage for driving the power MOSFET by the pulse signal.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]The present application claims priority from Japanese Patent Application No. JP 2007-044845 filed on Feb. 26, 2007, the content of which is hereby incorporated by reference into this application.TECHNICAL FIELD OF THE INVENTION[0002]The present invention relates to a switching power supply. More particularly, the present invention relates to a technique effectively applied to power factor correction of an alternating input current.BACKGROUND OF THE INVENTION[0003]To perform rectification and smoothing to obtain a direct current from an AC power supply, a configuration using a diode bridge and a smoothing capacitor is simplest. Meanwhile, since this configuration results in a rectifier circuit of so-called capacitor input type in which an input current flows only when whose power supply voltage is near the peak, which causes a lowering of power factor or an increase of input harmonic. Since the matter of input harmonic current is regulated ...

Claims

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Application Information

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Patent Type & Authority Patents(United States)
IPC IPC(8): G05F1/40
CPCH02M1/4225H02M2001/0009Y02B70/126Y02B70/10H02M1/0009
Inventor KANOUDA, AKIHIKOYOKOTA, KENICHI
Owner RENESAS ELECTRONICS CORP